Generally, image pickup devices are used to take photographs or make video conferences. With increasing development of the digital techniques, documents are gradually created as electronic files. Conventionally, the documents are scanned by scanning apparatuses and then saved as electronic files such as PDF (Portable Document Format) files. For most companies, the scanning apparatuses are essential apparatuses. For some companies, the scanning apparatuses are not necessarily purchased. In other words, the applications of the scanning apparatuses to create electronic files are limited.
Recently, a method has been proposed for creating electronic files of simple documents (e.g. single-sided papers or business cards) without the need of using the scanning apparatus. In this method, an image pickup device is served as a peripheral device of the computer to capture the image of the document. The captured image of the document is saved as an electronic file. This electronic file is an image file such as a JPEG (Joint Photographic Experts Group) file.
As known, optical character recognition (OCR) is a process of capturing an image of a document and then extracting the characters from the image. Recently, it is possible to analyze images that are captured from the image pickup device by the OCR technique and saved as image files. As a consequence, individual characters or signs contained in the images files are recognized and converted as editable text files. Since the associated OCR techniques are well established, the image pickup device is gradually adopted to obtain electronic files of the documents.
However, when an image pickup device is used to shoot a business card, some difficulties possibly occur. For example, it is critical to hold the document steady. Since the common web camera (i.e. an image pickup device) installed in a computer has a preset focal length of approximately 60 centimeters, this kind of image pickup device is feasible to shoot the facial expression of the user rather than the document. When the user wants to shoot an article contained in a document by the image pickup device, if this document is held by the user's hand, the document should be moved to the focusing position (i.e. an optimal shooting position). Due to the rocking of the user's hand, the obtained document image is usually blurred. For avoiding moving the document by hand every time and preventing from obtaining a blurred document image due to the rocking of the user's hand, a static document stand is used for holding the document steady to obtain a sharp document image. It is noted that the location of the document stand is dependent on the focal lens of the image pickup device. The use of the document stand, however, incurs another problem. That is, the document stand should be placed in a fixed location. In a case that the document stand is used in other places, the user should carry the document stand, which is very troublesome to the user.
For convenience, the document is directly placed on a working plane (e.g. a desk plane) without the need of the document stand. In addition, the notebook computer having an image pickup device is used for shooting the document. After the document is placed on a proper location of the working plane, the upper cover of the notebook computer is rotated such that the image capturing device installed on the upper cover is close to the document. Meanwhile, the document may be shot by the image capturing device, and thus the document image is acquired. However, when the image capturing device of the notebook computer is used to capture the image of the document placed on the working plane, some drawbacks also occur. The common drawback is occurrence of a distorted image. If the shooting range of the image capturing device is insufficient, the image captured by the image capturing device for a single time is usually incomplete. For solving this drawback, the user usually shoot document for two times in order to obtain two incomplete images. By means of image processing techniques, these two incomplete images are combined together. In other words, after the upper-half portion of the document is shot by the image capturing device, the document should be moved to have the lens of the image capturing device align aligned with the lower-half portion of the document in order to shoot the lower-half portion. Since there is no reliable reference tool or reference point on the document, the document is readily aslant during movement of the document. Consequently, the document posterior to movement fails to be parallel with the original document or located at the same level as the original document. Due to the distorted image, the image of the lower-half portion of the document is distorted and fails to be successfully combined with the upper-half portion of the document. For obtaining a sharp image, it is necessary to re-shoot the document.
Therefore, there is a need of providing an image pickup system for judging whether the document is at the optimal shooting position without the need of using a document stand.